1. Field of the Invention
The present invention relates to the medical field and particularly to orthopaedics and traumatology for the correction of limb bone deformities and deficiencies. More particularly, the invention relates to a surgical implant or staple and method for repairing bones and/or correcting limb inequality and most preferably the invention relates to methods and staples for correcting bone deficiencies by suppressing and/or inducing the growth of the epiphyseal plate in the bone. Additionally, the invention relates to staples with enhanced osseous integrating means capable of being easily removed from the bone even once integrated. Furthermore, the invention relates to staples for preventing the perichondrium and the periosteal vascular ring from damage when installing the staple into the bone.
While more specific reference to the control of growth plate or epiphyseal plate will be made in the present disclosure and drawings, the bone implant and methods of the invention are not restricted to this specific application but they may be applied to any other field where a prosthesis, a fixation device, etc. is to be secured into a bone or a broken bone is to be repaired by joining its broken pieces. In addition, the term “patient” is applicable either to animals or human beings.
2. Description of the Prior Art
Length discrepancies and angular deformities of the limbs are quite frequent among children and provoked by several causes such as congenital, post-trauma, post-infection, oncologic causes, etc. The need exists for correcting these abnormalities because of function and aesthetic reasons. The treatment of some of these childhood deformities is based on the concept of mechanically suppressing growth.
Bone staples are well known in the orthopaedics and traumatology, such as in techniques for correcting angular deviations of limbs, genu valgum for example, by unilateral restriction of the growth plate.
For correcting angular deviations the mechanical suppression can be obtained by temporary using metal staples across the growth plate, at unilateral locations, at the convex side of the deformity, for example. The staples are removed once the correction has been reached.
For correcting length abnormalities, the lengthening of the bone is obtained by using an external fixator and the shortening of the limb is obtained by arresting or suppressing the growth plate at even locations around the bone.
The technique of mechanical suppression by temporary using an external fixator is carried out by installing the fixator in the limb, on the concave bone side, for producing a slow stretching of the growth plate. This mechanical technique is known as epiphyseal distraction.
More precisely, epiphyseal distraction is a surgical technique that is widely used to lengthen an abnormal bone or correct physeal deviations prior to growth plate closure. This technique, also called “chondrodiatasis”, involves slow, gradual, symmetric distraction of the growth plate. The term “hemichondrodiatasis”, on the other hand, is used to refer to the technique of asymmetric distraction of the growth plate for correction of epiphyseal-diaphyseal deviations.
Since the use of external fixators for the above described mechanical suppressing techniques has shown to be expensive as well as traumatic and cumbersome for the patient, and the fixator leaves unsightly scars, the use of this device has not widely and intensively imposed. It would be desirable to use staples for these techniques, however, the staples are affected by several disadvantages and drawbacks that caused them to be not widely imposed in the medical field.
As it was stated above, angular deviations or deformities and length discrepancies of the limbs, for example, are often treated with staples. After staples are placed across a growth plate, further growth of this plate increases the pressure on the inner surfaces of the staple legs. This increased pressure, which has been measured about 1 Mpa, slows bone growth within and near the staple, i.e. in the region between the legs, and, simultaneously, forces the staple legs apart. This pressure from the cartilage plate, together with the legs moving away from each other, causes the legs to be extruded and expelled out from the bone thus loosing the grip in the bone.
Another drawback the physicians have found with the use of staples is that the same do not work satisfactorily because the bone growth is not restarted afterwards, thus producing the appearance of opposite deformity due to the constant growth of the cartilage of the side that was not operated upon. An explanation for this effect is that, presumably, a damage is inflicted on the perichondrium or the perichondrial vessels when the staples are inserted into physis. Generally, the staples are provided with reinforcing squares at the inner side thereof, that is at the inner corners formed by the connection between the cross bar and legs. As the staple is hammered up to abutting the external surface of the bone, the reinforcements, as well as the flat bridge or cross bar enter into contact with the growth plate and damage the perochondrium and the perichondrial vessels, this being the cause of the undesired epiphysial arrest.
As indicated above in connection with one of the drawbacks of using staples, the pressure exerted by the growing cartilage plate causes the staple legs to open, extrude and slide out of the bone. Many staples of the prior art has attempted to prevent the staple from sliding out the bone by providing the staple legs with barbs or protrusions to enhance the anchoring of the legs into the bone mass. However, when deformation has been corrected and the temporary staple must be removed from the bone, the anchorage of the legs into the growing bone mass, that is desired at the time the stable is to be retained into the bone, is a bar or obstacle at the time the staple must be removed. In effect, this firm osseous anchorage prevents the staple from being easily removed by normal forces and operations.
It would be therefore desirable and convenient to have a bone staple:
capable of accommodating to the growing force of the cartilage plate,
capable of being firmly retained and anchored into the bone to prevent the sliding out effect but capable of being easily removed when necessary, particularly after osseous anchorage, and
capable of being hammered into the bone without the bridge or cross bar of the staple damaging the perochondrium, the perichondrial vessels, and/or any other part of the bone.